I. Field of the Invention
The present invention relates generally to wireless telephone systems, and more particularly to radio frequency signal couplers for wireless telephones. The invention further relates to a technique for coupling multiple or different frequencies to wireless device antennas, when such devices are used with receptacles or cradles in vehicles.
II. Description of the Related Art
Wireless telephones are in widespread use because of the convenience they afford in personal communications. Wireless telephone technology continues to advance, producing better wireless communication systems while older systems nevertheless remain in use.
For example, earlier wireless telephone systems use analog communication principles and a communication frequency band of around 800 MHz (the so-called "cellular" frequency band), whereas more recent systems have been introduced that use digital communication principles in a frequency band around 1900 MHz (the so-called "personal communication system", or PCS, frequency band). In some geographic regions, both of these systems are in use, and in some circumstances the older systems that operate around 800 MHz have been or will be converted to use digital communication principles.
In any event, because of the different frequencies used by different wireless telephone systems, the frequency at which a user's wireless telephone must operate might change from region to region, system to system, or service provider to service provider. Indeed, some users in a given region might require telephones that operate at a first frequency while other users in the same region must communicate using a second frequency. In some instances, more than two frequencies might be in operation in a single area.
Recognizing the above-mentioned problem, it is recognized that it is desirable to provide wireless telephones that can communicate using one of at least two frequencies (and perhaps more), so that the telephones can be used in conjunction with more than one system. In other words, the present invention recognizes that it is desirable that one wireless telephone model be useful in more than one communication system, to increase the operational flexibility of the telephone. As a less desirable alternative, two telephones, each operating at a single respective frequency, can be provided.
At the same time, in order to increase or maintain appropriate concentration by a wireless device user on other tasks, device cradles have been developed for so-called "hands-free" communication. That is, wireless telephone cradles have be developed for use in vehicles, and other applications, which allow telephone use without unnecessary and unsafe operator distraction caused by holding the telephone. These cradles use an electromagnetic coupler to transfer signals between a telephone antenna and the cradle.
Among other considerations, the above factors, as inventively recognized herein, imply that a wireless telephone cradle or receptacle in a vehicle be capable of effectively extracting signals in at least two frequency bands from the antenna of a dual frequency wireless telephone, when the telephone is disposed in the cradle to facilitate hands-free operation. Stated differently, the telephone cradles with which many vehicles are equipped should be able to effectively couple signals from dual frequency telephone antennae to portions of the cradles that are associated with transmission and reception communication circuitry, regardless of which one of two communication frequencies the telephones might be using, to enhance communication flexibility and in some cases quality. The coupling should occur with relatively low loss.
Accordingly, it is a purpose of the present invention to provide a telephone cradle for a vehicle that effectively extracts signals in more than one frequency band from a telephone antenna. Another purpose of the present invention is to provide a telephone cradle for a vehicle that effectively transfers signals in more than one frequency band to and from a telephone antenna, and that is easy to use and cost-effective to manufacture and implement.